Question

\(A=\frac{10}{20}+\frac{10}{80}+\frac{10}{176}+\frac{10}{308}+\frac{10}{476}+\frac{10}{680}\)

Answer 1

Mình làm luôn, koghi lại đề

A=\(\frac{5}{10}+\frac{5}{40}+\frac{5}{88}+\frac{5}{154}+\frac{5}{238}+\frac{5}{340}\)

A=\(\frac{5}{2.5}+\frac{5}{5.8}+\frac{5}{8.11}+\frac{5}{11.14}+\frac{5}{14.17}+\frac{5}{17.20}\)

A=\(\frac{5}{3}\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{17}-\frac{1}{20}\right)\)

A=\(\frac{5}{3}.\left(\frac{1}{2}-\frac{1}{20}\right)\)

A=\(\frac{5}{3}.\frac{9}{20}\)

A=\(\frac{3}{4}\)